点扩散函数的改进倾斜刃边重建的高精度估计

基于现有刃边法提出了一种不受刃边倾角限制的点扩散函数高精度估计算法,通过改进刃边拟合、样本去噪与防走样重采样优化边缘扩散函数重建过程,并采用高斯函数拟合点扩散函数得到高精度PSF估值。试验表明,相较于现有刃边法,本文方法的估计精度与稳定性有显著提高。     

优化点扩散函数估计与稀疏约束的图像盲复原

在卫星光学图像盲复原问题中,点扩散函数的估计和复原模型选择对结果影响很大。针对点扩散函数模板估计困难的问题,该文在分析图像中近似点状地物成像特点的基础上,提出了基于点状地物信息的椭圆抛物面模型点扩散函数估计方法,得到较好的点扩散函数模板;针对图像噪声对复原的影响问题,采用能够分离图像的信号和噪声的归一化稀疏约束模型进行盲复原。利用"吉林一号"卫星图像进行了实验。结果表明:该文提出的优化点扩散函数估计方法可行,盲复原后图像质量得到了提高。     

用蒙特-卡罗方法计算大气点扩散函数

大气效应的纠正是一个仍未被彻底解决的定量遥感问题,随着遥感器空间分辨率的不断提高,各种斜视星勒遥感不断涌现,寻找交叉辐射项的修正方法日显迫切,该文应用蒙特－卡罗（Ｍ－Ｃ）方法求得不同大气条件下的点扩散函数图形,结果显示：（１）大气状况对点扩散函数的形状、目标像元的贡献率有不可忽略的影响;（２）一次散射的假定将导致背景像元的贡献率,其绝对误差最大可达７％,其相对误差最大可达４０％;（３）斜视条件下与     

利用点扩散函数进行DEM尺度转换

利用点扩散函数的图像模糊特性,提出了一种利用点扩散函数进行数字高程模型(digital elevationmodel,DEM)尺度转换的方法,即以不同尺度的点扩散函数作为模板,通过其与原始DEM的卷积实现不同分辨率DEM的尺度上推。设计了DEM尺度转换的评价指标,该指标包括高程统计特征、空间自相关特性及地形结构特征等。以陕北和晋中两种不同地形的1∶1万5 m格网分辨率DEM为研究数据,对此方法进行了分析验证,并与常用的最邻近、双线性以及立方卷积等方法进行了对比。     

一种优化的基于倾斜刃边的点扩散函数重建方法

已有的倾斜刃边法受边缘亚像素定位精度、边缘扩散函数(ESF)样本质量及ESF曲线拟合方法的限制,点扩散函数(PSF)重建的稳定性和精度不高。为此,提出了一种优化的基于倾斜刃边的PSF估计方法,将梯度算子引入刃边直线拟合,对刃边边缘进行了高精度的亚像素位置修正;并采用基于移动窗口的ESF去噪及重采样方法精化ESF样本质量;最后通过高斯函数拟合得到稳健的PSF估计值。实验结果表明,改进算法的边缘直线拟合精度优化效果明显,且PSF重建精度较高,稳定性强。     

任意形状曲线刃边的点扩散函数估计方法

遥感图像的点扩散函数估计是降低光学模糊、提高质量的必要前提。倾斜直线刃边法受到靶标极大的限制。现有的曲线刃边估计法虽然克服了倾斜刃边法只能适用于直线刃边的缺点,但是会因坐标拉伸导致估计值误差偏大。利用移动窗口的思想,提出了一种基于投影法的任意形状曲线刃边法,并在理论上说明了可行性。试验验证过程中先进行线性拟合刀刃边缘点,再对选定窗口内一定行数或列数的灰度值运用投影法采样,并对不同采样窗口的采样中心进行对齐处理,剔除不适合的样本点后插值和重采样,最终得到估计的点扩散函数。对于曲率在0.001～0.01的刃边,在较强模糊下,峰值信噪比依旧能保持在35 dB以上,测得点扩散函数峰值的误差可以控制在20%以内。相比传统刃边法和曲线拟合法,峰值信噪比平均能提高10 dB以上,且具有一定的抗噪性。     

基于线扩散函数的高精度轮廓特征提取算法

提出了一种基于线扩散函数的运动目标高精度轮廓特征提取算法(LDFM)。对该算法提取轮廓边缘的精度和抑噪去伪方法进行了分析,并将其应用于飞机序列影像的轮廓提取中,取得了预期的实验结果。     

目标边缘保持约束的图像联合解卷积复原算法

针对图像复原过程中去噪与目标边缘特征保持之间的矛盾,该文提出了一种基于目标边缘保持的图像联合解卷积复原算法。首先,构建了一个目标边缘保持约束模型,实现对图像小梯度特征(噪声为主)的平滑、对图像大梯度特征(目标边缘为主)的保留,平衡复原处理过程中图像去噪与目标边缘保持之间的矛盾;然后,将目标边缘保持约束先验模型,引入MAP图像复原框架,提升MAP复原算法的可靠性和收敛性;最后,利用共轭梯度迭代优化计算过程,加快算法收敛速度。实验结果表明,该算法能较好地平衡图像去噪与目标边缘特征保持之间的矛盾,实现了图像高清晰复原。     

基于MATLAB图像处理工具箱IPT函数的遥感图像配准

遥感图像配准是遥感图像拼接、信息融合的基础,是对遥感图像定量应用和研究的关键环节.MATLAB的图像处理工具箱IPT(Image Processing Toolbox)提供有基于点特征进行图像配准的函数,利用这些函数可以方便快捷地完成图像之间的配准.论文首先对图像配准及基于点特征的遥感图像配准作了详细的介绍,然后对IPT中配准函数的语法格式作了详尽的分析,并对两幅遥感图像进行了配准操作,最后对该方法进行了结论性分析,阐明该方法的应用价值与可改进之处.     

贝叶斯原理在遥感影像恢复中的应用

总结了遥感影像数据获取、传输和存储过程中引起影像退化的原因.根据信号处理中的概率统计理论,推导出了一种可以不依赖目标成像模型的遥感影像去模糊算法.实验结果表明,该算法具有较强的影像恢复能力和抗噪能力,对于缺乏点扩散函数先验知识的模糊遥感影像更加适用.     

不受刀刃边缘倾角约束的遥感影像点扩散函数稳健计算方法

采用传统刀刃法提取PSF时,只有在刀刃边缘近似平行或垂直于采样方向情况下才能得到好的效果,这样限制了刀刃法提取PSF进行图像恢复的广泛应用。本文提出了一种稳健的基于倾斜刀刃的图像的PSF计算模型,不仅在提取理想刀刃状况下(与采样方向近似垂直或平行)与传统方法等价,而且对倾斜刀刃提取PSF进行图像恢复也能得到理想效果,所恢复的图像在峰值信噪比(PSNR),均方差测度(MSE)和信噪比(SNR)等方面,都要优于传统方法,利用任意倾角的刀刃边缘提取的PSF都可以基本达到理想刀刃所提取的PSF的效果,因而提高了刀刃法提取PSF进行图像恢复的鲁棒性和通用性。本文分别从理论和实践上论证了模型的有效性,并采用模拟实验数据和ADS40航空影像数据验证了方法的正确性。     

Kinematic precise point positioning at remote marine platforms

Precise kinematic differential positioning using the global positioning system (GPS) at a marine platform usually requires a relatively short distance (e.g. <500 km) to a land-based reference station. As an alternative, precise point positioning (PPP) is normally considered free from this limiting requirement. However, due to the prerequisite of network-based satellite products, PPP at a remote marine platform may still be affected by its distance to the reference network. Hence, this paper investigates this scenario by configuring rings of reference stations with different radii centered on a to-be-positioned marine platform. Particularly, we applied ambiguity resolution at a single station to PPP by estimating uncalibrated phase delays (UPDs). We used three rings of reference stations centered on a vessel, with radii of roughly 900, 2,000 and 3,600 km, to determine satellite clocks and UPDs independently. For comparison, we also performed differential positioning based on a single reference station with baseline lengths of about 400, 1,700 and 2,800 km. We demonstrate that, despite the increasing ring-network radius to a few 1,000 km, the overall change in accuracy of the satellite clocks that are used at the vessel is smaller than 0.02 ns, and the RMS values of differences between the three sets of narrow-lane UPD estimates are around 0.05 cycles only. Moreover, the kinematic positioning accuracy of PPP is affected by the increasing ring-network radius, but can still achieve several centimeters after ambiguity resolution when the vessel is over a few 1,000 km away from the ring network, showing better performance than that of differential positioning. Therefore, we propose that ambiguity-fixed PPP can be used at remote marine platforms that support precise oceanographic and geophysical applications in open oceans.     

一种提高精密单点定位实时性的方法

由于要获取PPP需要的精密钟差文件至少有2d的时间延迟,因此通过提取IGS当天发布的超快星历中的卫星钟差数据,并对钟差数据进行插值,将插值结果做成标准格式钟差数据文件应用到PPP中,可以将精密单点定位的实时性提高为3~9h。基于Bernese软件,采用生成的钟差文件以及当天的超快星历文件对大量实测数据进行PPP。结果表明,对于4h的观测数据,该方法解算精度达到厘米级;当观测时间大于6h时,解算精度基本能够稳定在1~5cm。     

一种加快BDS精密单点定位初始化的方法

由于BDS卫星的星座特性及卫星的轨道和钟差的精度影响,使得传统消电离层组合精密单点定位(PPP)的初始化时间较长。针对上述问题,文中对附加电离层约束的非组合精密单点定位算法进行研究。首先介绍非组合PPP算法,分析其与传统PPP的差异;其次分别利用CODE电离层格网产品,以反距离加权算法计算的站星电离层延迟、低阶球谐函数建立的区域电离层产品等作为先验信息对非组合PPP进行约束。通过MGEX观测网实测数据静态和仿动态计算表明,相比传统消电离层组合PPP,附加电离层约束的非组合PPP能够有效缩短初始化时间,同时能够获得高精度的定位结果。     

Integer ambiguity resolution in precise point positioning: method comparison

Integer ambiguity resolution at a single receiver can be implemented by applying improved satellite products where the fractional-cycle biases (FCBs) have been separated from the integer ambiguities in a network solution. One method to achieve these products is to estimate the FCBs by averaging the fractional parts of the float ambiguity estimates, and the other is to estimate the integer-recovery clocks by fixing the undifferenced ambiguities to integers in advance. In this paper, we theoretically prove the equivalence of the ambiguity-fixed position estimates derived from these two methods by assuming that the FCBs are hardware-dependent and only they are assimilated into the clocks and ambiguities. To verify this equivalence, we implement both methods in the Position and Navigation Data Analyst software to process 1 year of GPS data from a global network of about 350 stations. The mean biases between all daily position estimates derived from these two methods are only 0.2, 0.1 and 0.0 mm, whereas the standard deviations of all position differences are only 1.3, 0.8 and 2.0 mm for the East, North and Up components, respectively. Moreover, the differences of the position repeatabilities are below 0.2 mm on average for all three components. The RMS of the position estimates minus those from the International GNSS Service weekly solutions for the former method differs by below 0.1 mm on average for each component from that for the latter method. Therefore, considering the recognized millimeter-level precision of current GPS-derived daily positions, these statistics empirically demonstrate the theoretical equivalence of the ambiguity-fixed position estimates derived from these two methods. In practice, we note that the former method is compatible with current official clock-generation methods, whereas the latter method is not, but can potentially lead to slightly better positioning quality.     

GPS精密单点定位中对流层延迟处理方法研究

本文首先介绍了GPS精密单点定位技术,采用宽巷组合的方法得到观测方程。然后对精密定位中的误差改正作了简述,主要讨论了处理对流层延迟的Saastamoinen模型和Niell映射函数。提出用扩展卡尔曼滤波参数估计方法来处理对流层延迟,通过实例用Saastamoinen模型、Saastamoinen模型加Niell映射函数和扩展卡尔曼滤波参数估计三种方法对对流层延迟进行改正,结果表明该方法优于Saastamoinen模型。     

基于精密单点定位的GNSS时间同步方法研究

高精度时间服务是国家综合PNT(positioning,navigation,timing)体系的重要组成部分,在国防军事、移动通信、天文观测等领域中发挥着重要作用。论文采用全球导航卫星系统GNSS授时的方式,提出了一种基于精密单点定位(PPP)技术的时间同步方法。该方法根据PPP时间传递结果驾驭本地时钟,使本地时钟所表示的本地时间与基准时间同步,可以达到亚纳秒级的时间同步精度,并且具备全天候、全覆盖、高精度、低成本等优点。     

A method for improving uncalibrated phase delay estimation and ambiguity-fixing in real-time precise point positioning

In order to improve the performance of precise point positioning (PPP), this paper presents a new data processing scheme to shorten the convergence time and the observation time required for a reliable ambiguity-fixing. In the new scheme, L1 and L2 raw observations are used and the slant ionospheric delays are treated as unknown parameters. The empirical spatial and temporal constraints and the ionospheric delays derived from a real-time available ionospheric model are all considered as pseudo-observations into the estimation for strengthening the solution. Furthermore, we develop a real-time computational procedure for generating uncalibrated phase delays (UPDs) on L1 and L2 frequencies. The PPP solution is first carried out on all reference stations based on the proposed scheme, undifferenced float ambiguities on L1 and L2 frequencies can be directly obtained from the new scheme. The L1 and L2 UPDs are then generated and broadcasted to users in real-time. This data product and also the performance of the new PPP scheme are evaluated. Our results indicate that the new processing scheme considering ionospheric characteristics can reduce the convergence time by about 30 % for float kinematic solutions. The observation time for a reliable ambiguity-fixing is shortened by 25 % compared to that of the traditional ambiguity-fixed kinematic solution. When the new method is used for static reference stations, the observation time for ambiguity-fixing is about 10 min in static mode and only 5  min if the coordinates are fixed to well-known values.     

GPS星历精度对精密单点定位的影响

精密单点定位的实质就是利用精密星历和精密卫星钟改正来实现单机精密定位。本文简要地介绍了精密单点定位的原理及技术关键,在此基础上,分析了IGS目前提供的3种精密星历(IGF、IGR、IGU)的精度和时延性。根据实验数据进一步分析了3种精密星历对精密单点定位精度的影响。通过精度分析,得出利用IGS的超快星历也可以达到厘米级定位精度,为全球厘米级单站RTK提供了有益的参考。     

面向定量遥感的高分辨遥感综合定标场及其应用

蓬勃发展的信息化时代对于稳定精准的定量遥感信息获取提出了迫切需求.遥感对地物目标信息的精准获取,从根本上取决于对遥感载荷性能及其长期业务运行期间状态变化的综合定标."十一五"以来,中国科学院定量遥感信息技术重点实验室牵头国内优势单位,系统性设计实现了面向定量遥感的高分辨遥感综合定标技术体系,研建形成"包头高分辨遥感综合...